EDITORIALForests are managed according to the management plan and programme of a particular management unit. Management plans and programmes are drawn up on the basis of the Forest Act and the Forest Management Regulations. However, are the regulations of other laws and by-laws obeyed? These include, for example, the Nature Protection Act, the Environment Protection Act, the Act on Forest Reproductive Material, the Hunting Act, the Forest Fire Protection Act, the Water Act, the Act on Roads, the Physical Planning and Building Act, the State Measurement and Land Registry Act, the Act on Sustainable Waste Management, and the Regulation on Remittance of Trees, Marking of the Timber and Forest Row, the Regulation on Forest Fire Protection, the Regulation on Strictly Protected Species, the Regulation on the Collection of Wild Plants, and the Regulation on the Ecological Network. The management plan is coordinated with the regulations of the Forest Management Plan of the Republic of Croatia. All this is well known to forestry experts and particularly to those from the Forest Planning Department, who prepare and draw up management plans. Still, it is worth while reminding those less knowledgeable of the matter that timber as raw material for further processing is only one of the vast array of forest products. The basic documents used to formulate management plans clearly highlight the role of the forest and its non-market function, as well as the monetary compensation for this function. Yet, this compensation is the bone of contention for the majority of the citizens, who are generally unaware of forest functions. However, writing this reminder-introductory word and asking the question in the title is always prompted by some events from our surroundings that draw our attention. For several years now, pursuant to the Act on Compensation for and Restitution of Assets Taken under the Yugoslav Communist Regime, some forest areas have been returned to their former owners - in some cases these areas are relatively large. According to the Forest Management Act, in the case of changed ownership relations caused by the restitution of property based on a special Law and in the case of property exceeding 100 ha, it is necessary to revise the management plan. This is done by the company "Croatian Forests" Ltd, which has been entrusted with the management of state-owned forests, and must be approved by the corresponding Ministry through its expert commission. It is expected that the job is also performed by the "new-old" forest owners, because the Forest Act is binding for all forest owners. The forest management departments of "Croatian Forests" Ltd offer their services of formulating management plans to the new-old forest owners, but in their words, mainly unsuccessfully. We assume that these programmes are executed by some other licensed forestry companies. Hard to believe, but there have been cases of such jobs being entrusted to sawmill owners! Thus, the already familiar "acts of plundering" in private forests are continuing, but now over even larger areas. Trees are being mercilessly cut down, and it is evident that such acts are either approved by someone or that eyes are being shut to this practice. We would not want to incriminate anybody because we are not inspectors, but what we would like to do is, on the basis of indicators, warn the relevant ministry to undertake the required measures, and particularly the Chamber of Forestry and Wood Technology Engineers, to protect the seal of a licensed engineer from possible profanation. Otherwise, it would be interesting to know in what manner and where the raw wood material from private forests ends and in which processing stage it is found. We know that the majority of raw wood material of Croatian Forests Ltd is "distributed" to buyers at non-market prices, although even the small quantities sold on the market on the public bid principle show a considerable difference in the profit. However, the changes in the selling policy of state forests are a far cry from the desired and more realistic profit. The state - the owner, loses and private pockets of wood processors are filled on the pretext of retaining working places. The news in the press talking of higher prices of raw wood material is just a new administrative, and not a marketing measure. Several days ago we watched a TV programme on wood processing in Petrinja, and the first conclusion was that "it is the turn of Croatian Forests Ltd" to ensure raw wood material, in the same way it was demanded for similar production in Vukovar, naturally, at "favourable prices". What is this final production? Parquet, which, in the rational use of raw wood material represents a product of sawmill processing and the lowest stage of final timber processing. Veneer is a semi-finished product - raw material for further wood processing. There is no proper finalisation, and it is finalisation that generates the creation of added value and new working posts. Due to our non-market policy we export these instead of wood products in the highest finalising stage. It goes without saying that finalisation stimulates the accompanying industry (frames, glues, varnishes and similar) and ensures specialized training and employment to not only production workers but also wood technology engineers. Why is this so hard to understand?Editorial Board

SummaryThe paper presents the results of research on the survival and growth of several tree species which could be used to replace poplars in plantations if necessary. The experiment was established in the area of Valpovo Forest Office, in the Management Unit of Valpovačke Podravske Šume, forest area of Topolje, sub-compartment 23a. This locality is a typical example of poor growth and dieback of poplar plantations even after multiple restocking with poplar seedlings and tending. The experiment was set up according to the randomized block design, with six treatments in four blocks. The following stand forms were treated: A - pedunculate oak, B - narrow-leaved ash, C - black locust, D - pedunculate oak with common hornbeam, E - wild cherry with narrow-leaved ash, and F - wild cherry with common hornbeam. The experiment was established on November 18, 2000. Plant survival was recorded every year over a five-year trial monitoring period. During the winter of 2015, the height of all the trees was measured and the spatial position of live and dead individuals per subplot was determined. In terms of survival and height as indicators of plant growth and development, the best results were manifested by black locust, followed by narrow-leaved ash and pedunculate oak. The poorest results were achieved by wild cherry and common hornbeam. With regard to the micro-relief, the best survival was displayed by black locust, which grows equally well both in unsoaked micro depressions (niza) and on micro elevations (greda). Narrow-leaved ash and pedunculate oak survived better in micro-depressions. In general, wild cherry and common hornbeam showed poor survival irrespectively of the micro-relief. Research results confirm the hypothesis regarding the need to replace or substitute poplar plantations under changed site conditions towards a stand whose stand form is adequately suited to the terminal forest community of the study area - spreading elm and narrow-leaved ash with pedunculate oak (Fraxino-Ulmetum laevis Slavnić 1952). The procedure should be preceded by a detailed forest management plan which would, among other things, define the areas of micro-depressions and micro-elevations in a particular compartment. Micro-depressions and wet micro-elevations should be reserved for narrow-leaved ash, which showed very good results in the trial. Pedunculate oak displayed very good stability and vitality and should therefore be used in a mixture with narrow-leaved ash. Black locust proved to be suitable in all conditions, but it is recommended to use it over the driest and sandy soils which have abruptly remained without ground and floodwater.

SummaryWe studied the morphological variation and its correlation to the environment in a boreal tree species, Alnusincana (L.) Moench subsp. incana, across the Croatian continental and Alpine-Dinaric biogeographical regions. A total of seven grey alder populations from environmentally divergent habitats were included in the study. We combined descriptive and multivariate statistical methods by using morphological leaf traits and environmental features to examine the diversity and structure of grey alder populations. High phenotypic variation, and two distinct morphotypes were found: small-leaf in the Alpine-Dinaric region, and large-leaf in the continental region. We identified a biogeographical structuring of populations with a high level of among-tree variation within the populations. Multivariate phenotypic and environmental analysis confirmed the existence of small- and large-leaf ecotypes. Additionally, a lack of significant among-population variation within biogeographical regions was observed. Furthermore, we found that phenotypic divergence of the studied grey alder populations can be explained as a result of a significant level of isolation both by distance and by environment.

SummaryThe paper studies effects of two heavy thinnings on the increment and slenderness of various categories of trees and stability of the stand as a whole. The research was conducted on a permanent experimental plot in an Norway spruce (Picea abies /L./ Karst.) monoculture in Serbia. This monoculture was established with 5,000 seedlings per hectare on the site of mountain beech forest and the effects of heavy thinnings were investigated in the 33-40 and 41-50 age periods.To determine the thinning effects we compared current diameter increments (idt) and current height increments (iht) of dominant trees (D100 and D400) obtained by a detailed analysis of trees and of mean stand dominant trees (D100 and D400). At the stand level, we compared the current diameter (id), basal area (IG) and volume (IV) increments of all trees and of the same collective of aspirants in two periods after the thinnings, between the ages of 33 and 40, and between the ages of 41 and 50.The first thinning was carried out at the age of 32 when the dominant trees were 15 m tall and the next at the age of 40 when the dominant trees were above 20 m in height. They were both low (qd <0.85) and heavy selective thinnings (34-36% of the volume). A more significant increase in the diameter increment was recorded after the second thinning between the ages of 41 and 50. It amounted to 29.1% in aspirants and 36-42% in dominant trees (D100 and D400) compared to the period after the first thinning, i.e., between the ages of 33 and 40. The thinnings further contributed to the establishment of more favorable relations in diameter and height increments of the trees in the studied culture and thus improved their stability.

SummaryThis study presents results of the comparison of structural and production characteristics of managed and virgin European beech forests in Serbia. Five managed and three virgin European beech stands were studied. The aim of this research was to determine the impact of the previous forest management on the structural diversity and production characteristics of managed European beech high forests in Serbia. The observed stands are located in the mountainous range of 400 to 1200 meters above sea level in the areas with the most productive beech forests in Serbia. Structural characteristics were compared using the following parameters: Height curves, Diameter distribution, Gini index, Coefficient of variation, Slenderness coefficient and maximum dimensions of standing living and dead trees. Stand density and productive characteristics were studied using the following forest estimation elements: number of trees, basal area, volume, biomass, carbon stock, stand quadratic mean diameter, Lorey’s mean height and volume of dead wood. The greatest differences were found in the dimensions of the largest trees in managed and virgin beech forests (diameters at breast height and heights). Certain differences were found in the shape of Height curves and Diameter distribution and in the values of Slenderness coefficient. However, the Gini index and the Coefficient of variation show that these managed beech forests in Serbia substantially preserve the primeval structural diversity. The differences in the average value of most forest estimation elements of managed beech high forests in Serbia compared to virgin beech forests are statistically significant, which tells us that the previous management had a significant impact on the changes in the production characteristics of these forests in Serbia.

Summary Gypsy moth, Lymantria dispar was the dominat oak forest pest in Croatia untill 1960s. After this period population particularly in the continental part decreased with cyclical outbreaks every 10-11 years. Last two outbreaks occurred in 2003-2005, and in 2013-2014. In this study a new calculation of critical number of gypsy moth egg masses has been presented in order to estimate the risk of defoliation which is crucial for the decision about application of necessary control measures. The calculation shows critical numbers as number of egg mases per ha which differ from the previous calculations based on number of trees which carry at least 1 egg mass shown in percentages. Hitherto 5 Classes were known out of which the 5th was critical. This Class presented 50% of trees which carry at least 1 egg mas and it was assessed as critical. In such calculation the age of the trees was not taken in account although the amount of leaves in the canopy strongly depend on that. Furthermore the number of eggs in the egg masses was also ignored. New calculation is based on numbers of caterpillars which have the potential to defoliate an oak tree of different ages, obtained from literature. The average number of eggs in one egg mass was calculated out of 50 sampled and analysed egg masses. This data together with the normal distribution of oak trees per ha build the basis for the formula. Based on that 3 Categories were formulated which show the potential for defoliation and help to make the decision for applying control measures: Category I – control measures needed; Category II – control measures needed only if there is a special reason; Category III – no control measures needed. Critical numbers of old and new calculation have been compared in years of outbreaks. Results between new and old calculation show 25% difference which directly means 25% less area that needs treatment with insecticides. Although the new method has advantages there is still some limitation in the calculation considering that important variables are ignored. The real number of trees per ha and the actual number of intact caterpillars should be used for more accurate calculation and further reduction of forest area that needs protection. Future research should concentrate on precise calculations of leaf weight consumed by average caterpillar in the relationship to crown volume both for oak and common beech. These values in combination with the number of leaves in the particular forest would make the decisions on use of insecticides more accurate which would bring additional substantial financial savings.

SummaryDemand for high quality free satellite data is increasing. Currently the most popular and known mission is Landsat satellite mission. This mission ensures ground resolution of 30 m x 30 m. For some application, this ground resolution is not sufficient. Landsat mission, starting from the Landsat 7 satellite, collects panchromatic band that is used to increase resolution of images. This paper analyzes the impact of multispectral and panchromatic image fusion on unsupervised classification. Based on original recordings NDVI (Normalized difference vegetation index) is calculated. This indexed image is used as reference image for the purpose of further comparison. The original images of first four bands (blue, green, red and near-infrared) are sharpened using eighth (panchromatic) band gathered with Landsat 7 satellite. From this bands, based on forth and third band, NDVI is calculated. With this calculation it is conducted pansharpening of reference NDVI image. Images for classification was chosen by comparing obtained images. Selected images was classified with K-means unsupervised classification algorithm, and it was determined that image calculated with bicubic interpolation and sharpened with fast intensity-hue-saturation (FIHS) algorithm on previously sharpened bands represents the best solution.

SummaryWe analysed the role of some fuel bed properties on forest fire-spread rate based on the thermal energy balance upon which the well-known fire-spread rate model of Rothermel (1972) was developed, showing that neither fuel bed height, load or density directly influence the thermal energy balance. The influence of such parameters, often inferred from empirical descriptions of spread rate, must result from indirect effects on heat transfer mechanisms. The fraction of heat transferred from the flame to the unburned fuel depends mostly on fuel moisture content and is independent of spread rate and flame geometry. Because empirical models usually implicitly assume the underlying mechanisms of fire spread for describing fire behaviour, this study results can assist at idealizing and delineating future experiments and approaches.